Casey Chalem Anderson "Salt Marsh Blues" 12 x 12 oil on panel

Casey Chalem Anderson “Salt Marsh Blues” 12 x 12 oil on panel

Why is water blue?

I was looking out on the water the other day and could not believe how blue it was.  I’m still stunned that the color is so intense, so truly blue.  Compared to the sea the sky is pale, maybe half as vivid.  I’m wondering once again, what makes them blue and not another color?

So far researching the answer reveals that although related, the sky and water are blue for different reasons. The ocean looks blue because red, orange and yellow (long wavelength light) is absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned to your eyes and you see blue.

And then you have the impurities dissolved and suspended in sea water that influence the appearance of the color.  As the sea gets stirred up by currents, the tides and the wind we see endless variations of blue, green, and gray.

It is intrinsic to water’s very nature that while small amounts of water appear to be colorless, water’s tint becomes a deeper blue as the quantity of water increases. Have you noticed how clear the water is near the shoreline in shallow water versus the blue of deeper water?

The main explanation for why the sky is blue is the optical phenomenon called “Rayleigh scattering effect”, where blue light from the sun is scattered every which way. The atmosphere filled with small particles of dust and water, tends to scatter the shorter blue wavelengths of light to a greater extent than the longer red wavelengths of red light providing many variations of intense blue in our sky.

I’m sure there is so much more to understand, but a comprehension of these basics is enough to know that there will always be shifts and variety in the blues we can see at the seashore.

Until next time,


This month I will donate 10% of my sales to the Peconic Land Trust. I am a founding member of Plein Air Peconic, the artist group dedicated to helping the Peconic Land Trust conserve the natural beauty of the East End of Long Island.

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